1. Field of the Invention
The present invention relates to a graphic meter display device and method that can be utilized for a display on; for instance, a vehicle gauge board, and the like.
2. Description of the Related Art
A vehicle, like an automobile, is equipped with various meters; for instance, a speed meter, a tachometer, and others. In each of such meters mentioned above, an indicator needle put on a predetermined number plate is generally actuated by an electric motor, and the like, in accordance with a measured value, whereby the indicator needle that performs a physical turn is controlled so as to point a position of a tick mark corresponding to a measured value.
In the meantime, as described in connection with; for instance, Patent Document 1 to Patent Document 3, techniques for displaying a meter through use of a graphic display, have already been developed. Specifically, when there is used a display device, like a liquid-crystal display panel in which a plurality of pixels capable of individually controlling a display are two-dimensionally arranged, respective display elements making up a meter, such as an indicator needle and tick marks, can be displayed as a graphic display pattern that is a combination of a plurality of pixel displays. Accordingly, a physical indicator needle becomes unnecessary, and a drive unit for actuating an indicator needle also becomes unnecessary.
Patent Documents 1 through 3 disclose proposed techniques for switching between a normal indicator needle pattern and a special display pattern (motion blur) in response to a change in turning speed of the indicator needle to be displayed.    Patent Document 1: JP-A-2007-303894    Patent Document 2: JP-A-2007-309719    Patent Document 3: JP-A-2008-8637
Incidentally, when a meter is displayed by means of a graphic display, such as that mentioned above, the following processing is performed in reality. Since a number plate and tick marks of a meter usually assume shapes close to a circular geometry, a direction to be pointed by the indicator needle must be calculated in accordance with a measured value to be pointed. For instance, in the case of a tachometer that displays the number of revolutions (rpm) of the engine, a pitch of tick marks showing an angle variation on a display unit basis is set to; for instance, 0.0225 degrees/rpm, on premise that the tick marks are equidistantly spaced. In this case, when a measured value represents 2000 rpm, a direction of the indicator needle to be displayed is determined to be (0.0225 degrees×2,000 rpm)), so that a direction of 45 degrees is selected. A pattern of the indicator needle is rendered by use of a graphic display so as to point at a direction of 45 degrees from the predetermined position of the center axis of the indicator needle. However, when the graphic display, such as that mentioned above, is provided, the following problems are encountered.
1. An error sometimes occurs during calculation of a direction of the indicator needle to be displayed.
2. When a pattern of the indicator needle is graphically displayed along the thus-determined direction, the orientation of the pattern must be changed by calculation of a previously determined pattern. There may be a case where the pattern will be deformed during calculation.
3. When tick marks of the number plate are rendered in conformity with an angle, there may be a case where the tick marks will be rendered in a misaligned manner.
When the calculation error and the pattern deformation, such as those mentioned above, occur, a position pointed by an indicator needle to be displayed may go out of alignment with a position of a tick mark corresponding to an originally measured value, which in turn causes a display error. In order to diminish the possibility of occurrence of such a display error, it is necessary to adopt a high resolution display panel, to prepare a precise display pattern, and to enhance a degree of accuracy of calculation. This results in an increase in cost of the display device, which inevitably leads to an increase in burden of display processing.
Moreover, in the case of; for instance, a speed meter of an automobile, there are cases where tick marks are not spaced equidistantly in a low speed zone, or the like. In this case, it is necessary to calculate a direction of the indicator needle by application of a pitch value differing from a normal pitch value to the zone where the tick marks are not spaced equidistantly, which makes display processing complicate.
Further, when a meter is graphically displayed through use of a liquid-crystal display panel, or the like, a high degree of freedom is considered to be available in connection with a design to be displayed as a meter. In order to enhance a commodity value or visibility of the meter, a meter having a unique geometry is sometimes required to be designed. For instance, there is a conceivable chance of appearance of gauge boards assuming an oval shape and a polygonal shape.
However, even when a related art meter is graphically displayed, the display is based on the presumption that tick marks are spaced equidistantly as mentioned above. In addition, the indicator needle also has a constant length; hence, a specially designed meter, like an oval meter and a polygonal meter, cannot have been adopted. If such a design is adopted, there is a high likelihood of occurrence of a greater display error or deterioration of visibility.